Field
This invention relates to multi-rotor aircraft such as quad-rotors that are configured as an H frame and to control units and methods for the craft.
Background
Quad Rotors or Quad rotor helicopters, classified as rotorcraft, are popular particularly in hobby craft for their stability and versatility of radio control (RC). Conventional quad-rotors (including multi rotors with 4, 6 or 8 rotors) have 4-8 rotor legs extending from a central member (in a cross configuration or structure) to which the rotor is attached. They generally have separate motors for each rotor. Each propeller is connected to the motor through reduction gears or directly to the motor shaft. All the propellers axes of rotation are fixed and parallel. Furthermore, they have fixed-pitch blades and their air flow point downwards (to get an upward lift). Thus, the structure is quite rigid and only the propeller speeds can be varied. Pairs of propellers rotate counterclockwise, while other propellers rotate clock-wise.
This configuration of opposite rotational direction and the opposing torques removes the need for a tail rotor that is needed in the standard helicopter structure). Conventional quad rotors generally use fixed pitched propellers. Two will spin clockwise and the other two will spin counter clockwise. By precisely and accurately spinning these four propellers at different speeds, all the common directional movements of a standard helicopter are attainable—hover, forward/backward movement, left/right movement, and yaw (turn rate) movement.
Some multi rotor design have as little as 3 propellers arranged in a triangle configuration and some up to six arranged in a hexagonal configuration and even eight (Octocopters). Because of their fixed propeller design multi-rotors, aircraft generally cannot sustain inverted flight or achieve advanced aerobatic containing “inverted” lift elements. The present invention overcomes many of the restriction of fixed pitch multi rotor craft.